rhododendron

Rhododendron is a genus of flowering shrubs and small trees in the heath family, Ericaceae. It includes azaleas and comprises many species and hybrids. Members range from evergreen to deciduous and from low shrubs to large shrubs or small trees. Leaves are typically simple, alternate, and leathery; many evergreen species have glossy foliage. The flowers are borne in large racemes or trusses and are often tube- or bell-shaped, with five lobes. Color variation includes white, pink, red, purple, and yellow. Bloom time varies by species, most flowering in spring, with some cultivars repeating in summer.

Rhododendrons are native to Asia, Europe, and North America, with greatest diversity in the Himalayas and southeastern Asia. They generally prefer acidic, well-drained soils rich in organic matter and partial shade, though some species tolerate sun with enough moisture. They require protection from strong winds and winter sun in cold climates. In cultivation, use acid-loving plant fertilizers and avoid lime. Pruning is typically done after flowering for evergreen rhododendrons; azaleas may be pruned after bloom or in late winter.

Many rhododendrons contain grayanotoxins in leaves and nectar; ingestion by humans or animals can be toxic, and honey produced from rhododendron nectar can cause illness in some cases. The genus is valued ornamentally for its long-lasting blossoms and as a habitat or nectar source for pollinators. Some non-native species, notably Rhododendron ponticum, can become invasive in certain regions.